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mark_m

Extra slow firing schedule for heavy pots

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I'm firing an L&L kiln with an LT3140 controller. Am not acclimated to these digital controllers and am firing a somewhat precious load with pieces up to 1/2" thick walls and some going to 1" on the feet. I want a very conservative schedule to be on the safe side. Have had problems in the past with the default slow bisque schedule.  Here is what I'm thinking:

180 rate 50 hold 8 hrs

210 rate 15 hold 1

213 rate 1.5 hold 1

650 rate 150

700 rate 50

1050 rate 150

1100 rate 80

1655 rate 150

Cone 06 rate 80 hold 1

This will be my first programmed schedule - part of me still wishes I just had knobs to turn but I know this will be so much more convenient when I'm used to it... Thanks for any thoughts!

-Mark M

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I don't think you're going to get any benefit in climbing super slow from 180 to 213. You're also putting too much faith in the ability of a controller to do super slow climbs. You might get regular temperature differences of 15 degrees during any climb. I wouldn't mess with rates less than 50 degrees per hour. Slower than that you're just wasting time. Better to get to the temp and hold. I would just do a long preheat at 180F, then climb at 75/hour all the way up. It will take about 24 hours after the preheat, but better safe than sorry.

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Thanks Neil. I am running a program kind of integrating your feedback with my schedule, i.e. still slowing down a bit more for chemically combined water and quartz inversion. Thanks very much for your thoughts!

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Mark, your work sounds a lot like mine.  I have texture sprig attachments, added feet, joinery and  lots of (paper) slip work.   Some pieces as big as 25lbs wet.   What I have found most effective is a substantial time under plastic to equalize the moisture before drying.  Then it dries  under bath towels.  The final step is a couple of days in the sun.  Using that, this is my bisque schedule.

40 degrees per hour to 120

hold 1 hour

80 degrees per hour to 200

hold 1 hour

250 degrees per hour to 1000

no hold

300 degree per hour to 1823 (cone 06)

It's 5 hours from start to closing the lid (propped open about 3" for burn out)

Very close to 10 hours complete.  I don't have breakage with this routine unless I miss guess how long a piece is in any phase.  It seems to me this is the best compromise between too slow and too fast.

 

 

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On 11/17/2019 at 8:06 AM, CactusPots said:

Mark, your work sounds a lot like mine.  I have texture sprig attachments, added feet, joinery and  lots of (paper) slip work.   Some pieces as big as 25lbs wet.   What I have found most effective is a substantial time under plastic to equalize the moisture before drying.  Then it dries  under bath towels.  The final step is a couple of days in the sun.  Using that, this is my bisque schedule.

40 degrees per hour to 120

hold 1 hour

80 degrees per hour to 200

hold 1 hour

250 degrees per hour to 1000

no hold

300 degree per hour to 1823 (cone 06)

It's 5 hours from start to closing the lid (propped open about 3" for burn out)

Very close to 10 hours complete.  I don't have breakage with this routine unless I miss guess how long a piece is in any phase.  It seems to me this is the best compromise between too slow and too fast.

 

 

Thanks - I got through that last firing ok, will compare  your schedule to what I ended up with!

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If I'm really nervous about a piece I'll run the first part of the schedule, to 200 degrees, shut it off closed and then run the schedule as normal.  I think you could run that on a pretty green and big piece and get away with it if you needed it for a load.

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